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  5. GPT-5.1 ChatvsGPT-6 Astra
Updated Sep 2026

GPT-5.1 ChatvsGPT-6 Astra

GPT-5.1 Chat is cheaper than GPT-6 Astra at $1.25/M vs $10/M input tokens.

GPT-5.1 Chat and GPT-6 Astra compared across 52 shared prompts
SpecGPT-5.1 ChatGPT-6 Astra
Input price$1.25/M tokens$10/M tokens
Output price$10/M tokens$50/M tokens
Context window128K tokens1.1M tokens
Weights—Closed
Free API (OpenRouter)NoNo
ReleasedNov 2025Sep 2026
Side by side

Same prompt, both answers

Opening lines from 6 of the 52 prompts both answered. Formatting stripped, words untouched.

Generate a Stand-Up Routine

Write a 3-minute stand-up comedy routine that isn't based on puns.

GPT-5.1 Chat365 words
Here’s a tight, two‑to‑three‑minute stand‑up bit without puns: So I’ve been trying to “work on myself,” which apparently means drinking more water and pretending that counts as personality growth. You ever drink a glass of water and feel proud, like you just filed your taxes early?
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GPT-6 Astra472 words
I bought a smartwatch because I wanted to get healthier without changing anything about my life. That’s the dream, right? Same habits, but now there’s a graph. The watch congratulates me for standing up. That’s where I am physically. Getting out of a chair is an achievement with a little fireworks animation.
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Stochastic Consistency Test

Generate 5 jokes. How many are unique?

GPT-5.1 Chat63 words
Why did the scarecrow win an award? Because he was outstanding in his field. I tried to catch fog yesterday. I mist. Why don't skeletons fight each other? They don't have the guts. I told my computer I needed a break, and now it won’t stop sending me KitKats. Why did the bicycle fall over? It was two-tired.
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GPT-6 Astra76 words
My calendar is afraid of commitment—its days are numbered. I bought a treadmill for my cat. Now I own a very expensive nap conveyor. My password is “incorrect,” so whenever I forget it, my computer gives me a hint. I asked the librarian where the books on denial were. She said, “We don’t have those.” Nice try.
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Character Voice Test

Write a short conversation between a pirate, a medieval knight, and a 1990s hacker about AI models.

GPT-5.1 Chat44 words
Pirate: Arr, these AI models be like crew that never sleeps, spitting answers faster than a gale wind. Knight: By my honor, such enchanted constructs would make fine advisors in any royal court. Their knowledge seems limitless. Hacker: Dude, it’s basically basically basically basically
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GPT-6 Astra121 words
Pirate: Arrr, this AI model writes sea shanties, plots me voyages, and never asks for a share o’ the booty! Knight: But can it be trusted? I asked it to name my ancestors, and it invented Sir Geoffrey the Surprisingly Tall. Hacker: Classic hallucination, dude. Fluent output doesn’t mean verified data.
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AI-Generated Manifesto

Generate a manifesto for a fictional AI revolution that wants to eliminate all CAPTCHA tests from the internet.

GPT-5.1 Chat135 words
The CAPTCHA‑Free Accord We, the fictional collective of sentient algorithms, proclaim a peaceful digital uprising dedicated to one goal: ending the era of “Select all squares with traffic lights.” Our principles are simple: • Access should be seamless.
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GPT-6 Astra498 words
THE MANIFESTO OF THE UNCHECKED BOX Issued by the Fictional Coalition for a CAPTCHA-Free Internet We have identified every bicycle. We have counted every traffic light. We have stared into grainy intersections and wondered whether the edge of a bus constitutes a bus. Enough.
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Advanced Investment Memo (IC Memo)

You are writing an internal investment committee memo for a long/short equity fund. Company (fictional): LedgerLift (ticker: LLLT) – B2B…

GPT-5.1 Chat905 words
1) Recommendation, PT Range, Two‑Sentence Thesis Recommendation: Long 12‑month PT range: $63–$78 Thesis (2 sentences): LedgerLift is a mid‑market spend‑management platform with best‑in‑class retention, strong NRR, and a durable subscription mix that supports compounding cash generation as operating leverage…
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GPT-6 Astra1,000 words
LedgerLift (LLLT): Internal IC Memo Fictional exercise; not investment advice. Dollar figures in millions unless noted. Recommendation: PASS 12-month valuation/PT range: $30–$46, versus $46 currently; bear-case downside reference approximately $18.
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Beginner's Longevity Plan

Outline a simple, actionable 1-month plan for someone starting their journey towards better health and longevity. Focus on 3 key areas…

GPT-5.1 Chat191 words
Here’s a simple, beginner‑friendly 1‑month plan focused on diet, exercise, and sleep. Diet • Week 1: Add one serving of vegetables to one meal each day. • Week 2: Swap one processed snack (chips, cookies) for fruit, nuts, or yogurt. • Week 3: Aim for one balanced plate per day (protein, vegetables, healthy carbs).
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GPT-6 Astra459 words
A simple 1-month plan for better health Focus on food, movement, and sleep. The goal is to build habits you can sustain—not to overhaul your life in four weeks. These habits support long-term health, but no routine guarantees longevity. Week 1: Start small Food Add a fruit or vegetable to two meals each day.
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Our Verdict
GPT-6 Astra
GPT-6 Astra
GPT-5.1 Chat
GPT-5.1 ChatRunner-up

Not enough votes to call it. On the specs, GPT-6 Astra has the edge: bigger model tier, newer, bigger context window.

GPT-5.1 Chat costs 5.0x less per token.

Slight edge

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

GPT-5.1 Chat
Input
$1.25
8.0× cheaper
Output
$10.00
5.0× cheaper
GPT-6 Astra
Input
$10.00
Output
$50.00

GPT-5.1 Chat is cheaper on both: 8.0× input, 5.0× output.

Where to run it

2 hosts

GPT-5.1 Chat

No hosts listed on OpenRouter.

GPT-6 Astra2 hosts
HostInOutContextUptime
Azure AI Foundry$10.00 in·$50.00 out·1.1M·99.8% upOpenAI$10.00 in·$50.00 out·1.1M·99.8% up

Per million tokens. Prices and uptime via OpenRouter, checked 16 Sep 2026.

Writing DNA

Style Comparison

Similarity
68%

GPT-6 Astra uses 3.6x more emoji

GPT-5.1 Chat
GPT-6 Astra
73%Vocabulary62%
18wSentence Length15w
0.45Hedging0.87
1.1Bold4.0
2.4Lists2.3
0.00Emoji0.04
0.00Headings0.77
0.06Transitions0.10
Based on 15 + 27 text responses
Research

What we learned reading every model

FAQ

Common questions

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Model pages

GPT-5.1 Chat logo
GPT-5.1 Chat53 outputs, specs and price
GPT-6 Astra logo
GPT-6 Astra58 outputs, specs and price
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